A suit which is based upon a writing ought not to vary from the writing.

Explanation

(English-origin maxim.) A suit founded on a written instrument must conform to the terms of that writing — the plaintiff cannot vary from the document upon which he bases his claim.

Where this applies

• A landlord sues to enforce a lease but argues for terms that differ from what the lease actually says — the court holds the landlord to the written document.
• A plaintiff sues on a promissory note but claims the borrower owes more than the note specifies — the court limits recovery to the amount stated in writing.
• A contractor sues to enforce a construction agreement but tries to add work not described in the contract — the suit must conform to the writing it is based on.